As the inhalation of oxygen from the lungs spreads throughout the body, as you exhale in the air many substances are excreted in this way from the organism. Some can be detected during the breath test and allow conclusions about certain dysfunctions, especially of the stomach and small intestine.
Breath tests make use of the fact that bacteria present in the gastrointestinal tract split substances. The resulting products enter the bloodstream and from there to the lungs, where they are exhaled and can be measured. There are two groups of tests:
- C-breath tests: The 13C breath test measures the concentration of carbon dioxide that is produced, inter alia, during the decomposition of urea. The urea is labeled with 13C and is absorbed through the mouth. In the stomach, it is cleaved by urease, an enzyme of the bacterium Helicobacter pylori (which occurs in gastric ulcers), and then resorbed. This is how he gets into the body. Measured is the increase of the labeled carbon dioxide (13CO2) contained in the exhaled air. For special questions, the C-breath tests are also carried out with markers other than urea (13C octanoic acid, 13C sodium acetate or 14C glycocholate).
- H2 breath test: It measures the concentration of hydrogen (H2), a product of carbohydrate cleavage in the gut. Depending on which function is to be examined, a test substance with a specific sugar is administered. Lactose, sucrose, glucose, fructose, xylose or lactulose are given.
Advantages and disadvantages of breath tests
- Breath tests have the advantage that they are safe and not very stressful for the patient, so they can even be done in children. Especially the H2 breath tests are very accurate.
- However, patient involvement is required for the test to be meaningful. Both in the preparation (diet the day before, sober) and during the examination, the patient must be reliable and patient.
- A disadvantage is that a relatively high expenditure on equipment is necessary for the laboratories.
- Many of the tests are not meaningful shortly after antibiotic therapy or after examinations associated with colonic irrigation (eg, colonoscopy) - so it may take several weeks to maintain.